Meningitis B vaccines may fight the rise of super-gonorrhoea

A vaccine for meningitis B may stop the spread of antibiotic-resistant super-gonorrhoea.

We desperately need a vaccine for the sexually transmitted infection. Last week, the World Health Organization reported that 81 per cent of the 77 countries that have looked for antibiotic-resistant gonorrhoea found strains resistant to azithromycin, the main antibiotic used to fight the disease.

Two-thirds of these countries had strains that were resistant to one of two “last resort” antibiotics, cefixime or ceftriaxone. Some cases resist all three of these drugs, and are effectively incurable. This means that even people who are treated for the infection can continue to harbour and spread the bacteria.

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According to the WHO, only three new drugs to combat gonorrhoea are being tested in people. Even if these work, bacteria could evolve to evade them. A vaccine “will ultimately be the only sustainable way to achieve control” of gonorrhoea, the agency warns.

But so far, experimental vaccines have all failed. Remarkably, an existing licensed vaccine may do the trick – a finding David Fisman at the University of Toronto, Canada, describes as “incredible news”.

Meningitis link

Gonorrhoea is caused by Neisseria gonorrhoeae bacteria, which are closely related to Neisseria meningitidis, which cause meningitis B. Because the protein sequences of the bacteria that cause meningitis B and gonorrhoea are 80 to 90 per cent identical, immune reactions to one might affect the other.

We don’t know why, but outbreaks of meningitis B sometimes last for a decade or two before disappearing, as happened in Cuba and Norway in the 1980s, and in New Zealand in the 1990s.

A vaccine was tailor-made for each of these outbreaks using particles from the outer membrane of the bacterial strains responsible. In New Zealand, mass vaccination of more than 80 per cent of people under the age of 20 was found to have shortened the outbreak.

“I realised this was a natural experiment,” says Steve Black of Cincinnati Children’s Hospital in Ohio.

Analysing clinical records, Black and his colleagues found that of the 15,000 people in New Zealand who would have been offered the meningitis B vaccine, those who had it were 31 per cent less likely than those who didn’t to later contract gonorrhoea. Vaccinated people who did get gonorrhoea were 40 per cent less likely to develop a severe form of the disease.

Small effect, big difference

That may not sound spectacular, but this is the first time a vaccine has had any impact on gonorrhoea. And because it doesn’t spread easily – it requires sex, not just a sneeze – even a relatively small effect could have a big impact. Mathematical modelling has previously suggested that if all 13-year-olds were given a vaccine that only protected half of them, the prevalence of gonorrhoea in the population would fall by 90 per cent in only 20 years.

Other modelling has found that gonorrhoea is primarily spread by sex workers and men who have sex with many male partners. Such groups “are key to controlling gonorrhoea”, says Fisman. “It is likely to collapse epidemiologically if even a small fraction of the population is effectively vaccinated, or if a large fraction gets a vaccine with relatively low efficacy.”

It would make sense, says Black, to consider offering meningitis B vaccination to such groups now – although they are typically more difficult for doctors to reach with medical treatments.

Meanwhile, a meningitis B epidemic is under way in the UK, affecting up to 1700 children a year, with a tenth of those dying. In 2015, the UK became the first country to routinely vaccinate babies for meningitis B, and this vaccine contains the New Zealand strain. In 20 years, we may see whether this has had an unexpected and welcome side effect on gonorrhoea, says Black.